The present invention pertains to improvements in the field of waste oil treatment. More particularly, the invention is directed to an improved process for the treatment of waste oils to produce refined oils which are substantially free of heavy metal contaminants.
Canadian Patent No. 1,168,590 discloses a process for the treatment of a hydrocarbon load by ultrafiltration at high temperature. Use is made of ceramic membranes having a porosity of 50 to 250 Å and the ultrafiltration is carried out at a temperature between 100 and 350° C. Such a high temperature reduces the life of the membranes. Moreover, the filtration flow is very weak and the quality of the products obtained is not according to standards.
U.S. Pat. No. 6,024,880 discloses a method for treating used oil to remove ash and color contaminants therefrom, wherein use is made of a porous ceramic membrane. The pores of the ceramic material are in the shape of a funnel, which renders the filtration difficult. In addition, such a type of ceramic membrane does not permit an effective separation of heavy metal contaminants from the oil.